Head-up display device

ABSTRACT

A head-up display apparatus includes: a display unit, which includes a display cell and a first polarizing plate with a retardation layer arranged on an output side of the display cell, the first polarizing plate with a retardation layer including a polarizer and a first retardation layer in the stated order from the display cell side, and which is configured to output projection light; at least one reflector configured to reflect the projection light; a housing, which has an opening portion, and which is configured to store the display unit and the reflector therein; a cover member configured to cover the opening portion; and a second polarizing plate with a retardation layer, which is arranged on a housing inner side of the cover member, and which includes a polarizer and a second retardation layer in the stated order from the cover member side.

TECHNICAL FIELD

The present invention relates to a head-up display apparatus.

BACKGROUND ART

The driver of a vehicle performs driving while carefully viewing thefront through a windshield, and visually observing meters on aninstrument panel. That is, the line of sight of the driver moves towardthe front and the meters below. When the driver can view the meterswhile viewing the front, the movement of the line of sight does notoccur, and hence an improvement in drivability (finally safety) can beexpected. In view of the finding, ahead-up display apparatus has startedto be developed and put into practical use. In the head-up displayapparatus, a cover member configured to cover the opening portion of anoptical path is arranged for preventing the entry of foreign matter,such as dust, into a housing in which an optical system is stored.Further, a polarizing plate may be bonded to the cover member forpreventing an increase in temperature in the housing (specifically forpreventing the incidence of sunlight) (e.g., Patent Literature 1). Arelated-art head-up display apparatus has an insufficient commercialvalue because its concealability for the inside of its housing isinsufficient, and hence the inside is seen. Meanwhile, when an attemptis made to improve the concealability of the head-up display apparatus,its display brightness reduces, and hence its viewability becomesinsufficient.

CITATION LIST Patent Literature

-   [PTL 1] JP 2008-70504 A

SUMMARY OF INVENTION Technical Problem

The present invention has been made to solve the conventional problems,and an object of the present invention is to provide a head-up displayapparatus capable of simultaneously satisfying concealability for itsinside and display brightness.

Solution to Problem

A head-up display apparatus of the present invention includes: a displayunit, which includes a display cell and a first polarizing plate with aretardation layer arranged on an output side of the display cell, thefirst polarizing plate with a retardation layer including a polarizerand a first retardation layer in the stated order from a display cellside, and which is configured to output projection light; at least onereflector configured to reflect the projection light; a housing, whichhas an opening portion, and which is configured to store the displayunit and the reflector therein; a cover member configured to cover theopening portion; and a second polarizing plate with a retardation layer,which is arranged on a housing inner side of the cover member, and whichincludes a polarizer and a second retardation layer in the stated orderfrom a cover member side. The first retardation layer and the secondretardation layer each have an in-plane retardation Re(550) of from 100nm to 200 nm.

In one embodiment, the polarizers each contain an aromatic disazocompound represented by the following formula (1):

in the formula (1), Q¹ represents a substituted or unsubstituted arylgroup, Q² represents a substituted or unsubstituted arylene group, R¹seach independently represent a hydrogen atom, a substituted orunsubstituted alkyl group, a substituted or unsubstituted acetyl group,a substituted or unsubstituted benzoyl group, or a substituted orunsubstituted phenyl group, M represents a counterion, “m” represents aninteger of from 0 to 2, and “n” represents an integer of from 0 to 6,provided that at least one of “m” or “n” does not represent 0, arelationship of 1≤m+n≤6 is satisfied, and when “m” represents 2, therespective R¹s may be identical to or different from each other.

In one embodiment, the polarizers each have a thickness of from 100 nmto 1,000 nm.

In one embodiment, the head-up display apparatus is configured so thatan angle of reflection of the projection light output from the housingthrough the opening portion with respect to a windshield is from 10° to50°.

Advantageous Effects of Invention

According to the embodiment of the present invention, in the head-updisplay apparatus, the first polarizing plate with a retardation layerhaving the following feature is laminated on the output side of thedisplay cell: the first polarizing plate with a retardation layerincludes the polarizer and the first retardation layer in the statedorder from the display cell side of the display unit. In addition, thesecond polarizing plate with a retardation layer having the followingfeature is laminated on the housing inner side of the cover memberconfigured to cover the opening portion of the housing: the secondpolarizing plate with a retardation layer includes the polarizer and thesecond retardation layer in the stated order from the cover member side.Accordingly, the head-up display apparatus capable of simultaneouslysatisfying concealability for its inside and display brightness can beachieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic partial sectional view for illustrating a head-updisplay apparatus according to one embodiment of the present invention.

FIG. 2 is a schematic partial sectional view for illustrating a head-updisplay apparatus according to another embodiment of the presentinvention.

FIG. 3 is a schematic sectional view for illustrating an example of afirst polarizing plate with a retardation layer that may be used in thehead-up display apparatus of the present invention.

FIG. 4 is a schematic sectional view for illustrating an example of asecond polarizing plate with a retardation layer that may be used in thehead-up display apparatus of the present invention.

FIG. 5 is a schematic view for illustrating a relationship betweenprojection light in the head-up display apparatus of the presentinvention and a windshield.

DESCRIPTION OF EMBODIMENTS

Now, embodiments of the present invention are described. However, thepresent invention is not limited to these embodiments.

A. Overall Configuration of Head-Up Display Apparatus

FIG. 1 is a schematic partial sectional view for illustrating a head-updisplay apparatus according to one embodiment of the present invention.A head-up display apparatus 100 includes: a display unit 10, whichincludes a display cell 11 and a first polarizing plate 12 with aretardation layer, and which is configured to output projection light;at least one reflector (in the illustrated example, one reflector) 20configured to reflect the projection light; a housing 30, which has anopening portion 32, and which is configured to store the display unit 10and the reflector 20 therein; a cover member 40 configured to cover theopening portion 32; and a second polarizing plate 50 with a retardationlayer, which is arranged on the housing inner side of the cover member40. Although the one reflector 20 is arranged in the embodiment of FIG.1 , two reflectors 20 and 22 may be arranged like a head-up displayapparatus 101 illustrated in FIG. 2 .

Any appropriate configuration may be adopted as the display unit 10. Thedisplay unit is typically, for example, a liquid crystal displayapparatus. Therefore, the display cell 11 is, for example, a liquidcrystal cell. Any appropriate configuration may be adopted as theconfiguration (e.g., driving mode) of the liquid crystal cell.

In the embodiment of the present invention, as described above, thedisplay unit 10 includes the display cell 11 and the first polarizingplate 12 with a retardation layer. The first polarizing plate 12 with aretardation layer is typically bonded to the output side of the displaycell 11 via a pressure-sensitive adhesive. As illustrated in FIG. 3 ,the first polarizing plate 12 with a retardation layer includes apolarizer 124 and a first retardation layer 126 in the stated order fromthe display cell 11 side. The first polarizing plate 12 with aretardation layer may include a substrate 122 on the display cell 11side of the polarizer 124 as required like the illustrated example. Inthe embodiment of the present invention, the first retardation layer 126has an in-plane retardation Re(550) of from 100 nm to 200 nm. When thein-plane retardation of the first retardation layer falls within suchrange, the setting of an angle formed between the slow axis of the firstretardation layer and the absorption axis of the polarizer to apredetermined angle (described later) imparts, to the layer, a functionof converting the light output from the display unit into circularlypolarized light or elliptically polarized light. Such output light(circularly polarized light or elliptically polarized light) isconverted into linearly polarized light by the second retardation layerof the second polarizing plate with a retardation layer to be describedlater, and is discharged from the opening portion to the outside of thehousing. Details of the first polarizing plate with a retardation layerare described later in the section C together with the second polarizingplate with a retardation layer. The term “Re(λ)” as used herein refersto the in-plane retardation of a film measured at 23° C. with lighthaving a wavelength of A nm. Therefore, the term “Re(550)” refers to thein-plane retardation of the film measured at 23° C. with light having awavelength of 550 nm. When the thickness of the film is represented by d(nm), the Re(λ) is determined from the expression “Re=(nx−ny)×d” where“nx” represents a refractive index in the direction in which arefractive index in the plane of the film becomes maximum (that is, aslow axis direction), and “ny” represents a refractive index in thedirection perpendicular to the slow axis in the plane (that is, a fastaxis direction).

Any appropriate configuration may be adopted as the reflector 20 (and,if present, the reflector 22). The reflector 20 has, for example, amirror portion and a mirror holder configured to hold the mirror portionat a predetermined position in the housing 30. The mirror portion may bea plane mirror, or may be a concave mirror. In the illustrated example,the concave mirror is adopted. The use of the concave mirror enablesenlarged display of a video to be projected. The radius of curvature ofthe concave mirror may be appropriately set in accordance with, forexample, a purpose and the size of the video to be projected. When thereflector 22 is arranged, the reflector 22 may be, for example, a planemirror (cold mirror) configured to transmit only an infrared ray and toreflect a visible ray and UV light.

The housing 30 is a box-shaped member having an internal space capableof storing the display unit 10 and the reflectors 20 and 22. The housing30 typically has the opening portion 32, and the projection light outputfrom the display unit 10 through the opening portion 32 is discharged tothe outside of the housing 30. The housing 30 may include anyappropriate material. A preferred constituent material therefor is, forexample, a material that hardly undergoes a temperature increase due toirradiation with sunlight, and that is easy to form. Specific examplesof such material include an acrylic resin, an epoxy-based resin, apolyester-based resin, a urethane-based resin, a polyolefin-based resin,a fluorine-based resin, and a phenoxy-based resin. The housing 30 may beincorporated in a part of an automobile, or may be a member independentof an automobile. For example, a dashboard of an automobile may be usedas the housing.

The cover member 40 is a plate-shaped member configured to cover theopening portion 32 of the housing 30 so that dust does not enter theinside of the housing 30. The cover member 40 is typically transparent,and the projection light reflected from the reflector 20 passes thecover member 40 to be discharged to the outside of the housing 30.Details of the cover member are described later in the section B.

In the embodiment of the present invention, the second polarizing plate50 with a retardation layer is bonded to the housing inner side of thecover member 40 via a pressure-sensitive adhesive. As illustrated inFIG. 4 , the second polarizing plate 50 with a retardation layerincludes a polarizer 54 and a second retardation layer 56 in the statedorder from the cover member 40 side. The second polarizing plate 50 witha retardation layer may include a substrate 52 on the cover member 40side of the polarizer 54 as required like the illustrated example. Inthe embodiment of the present invention, the second retardation layer 56has an in-plane retardation Re(550) of from 100 nm to 200 nm. When thein-plane retardation of the second retardation layer falls within suchrange, the setting of an angle formed between the slow axis of thesecond retardation layer and the absorption axis of the polarizer to apredetermined angle (described later: further particularly preferablyaround 45°) imparts, to the layer, a function of converting linearlypolarized light into circularly polarized light or ellipticallypolarized light, or a function of converting circularly polarized lightor elliptically polarized light into linearly polarized light. As aresult, the projection light (circularly polarized light or ellipticallypolarized light) output from the display unit (liquid crystal displayapparatus) can be satisfactorily converted into linearly polarized lightand discharged to the outside of the housing 30. Further, natural lightfrom the outside is converted into circularly polarized light orelliptically polarized light by the second retardation layer, and whenthe circularly polarized light or the elliptically polarized light isreflected in the housing, its rotation direction is reversed. Suchcircularly polarized light or elliptically polarized light that has beenreflected (whose rotation direction has been reversed) is absorbed bythe second retardation layer, and hence its discharge to the outside ofthe housing can be substantially prevented. As a result, the brightnessof the projection light from the display unit to be discharged to theoutside of the housing can be maintained at a high level, and theviewability of the inside of the housing can be markedly reduced (i.e.,concealability for the inside of the housing can be made extremelyexcellent). In other words, a head-up display apparatus capable ofsimultaneously satisfying concealability for its inside and displaybrightness can be achieved by incorporating each of the first polarizingplate with a retardation layer (the first retardation layer) and thesecond polarizing plate with a retardation layer (the second retardationlayer) into a predetermined position of the head-up display apparatusunder a predetermined state. Further, when the second polarizing platewith a retardation layer is arranged, the incidence (passing) of thesunlight can be suppressed by the polarizer of the second polarizingplate with a retardation layer. Accordingly, the heat resistance of thehead-up display apparatus can be improved. Details of the secondpolarizing plate with a retardation layer are described later in thesection C together with the first polarizing plate with a retardationlayer.

In the embodiment of the present invention, the first polarizing platewith a retardation layer and the second polarizing plate with aretardation layer are typically arranged so that the absorption axes oftheir respective polarizers are substantially parallel to each other.Further, the first polarizing plate with a retardation layer and thesecond polarizing plate with a retardation layer are typically arrangedso that the slow axes of their respective retardation layers aresubstantially perpendicular to each other. When the first polarizingplate with a retardation layer and the second polarizing plate with aretardation layer are arranged so as to form such axial angles, thefunctions of mutually converting linearly polarized light and circularlypolarized light or elliptically polarized light exhibited by the twopolarizing plates with retardation layers can be made sufficient. Theexpressions “substantially parallel” and “approximately parallel” asused herein each include a case in which an angle formed between twodirections is 0°±7°, and the angle is preferably 0°±5°, more preferably0°±3°. The expressions “substantially perpendicular” and “approximatelyperpendicular” as used herein each include a case in which an angleformed between two directions is 90°±7°, and the angle is preferably90°±5°, more preferably 90°±3°. Further, the simple expression“perpendicular” or “parallel” as used herein may include a state inwhich two directions are substantially perpendicular, or substantiallyparallel, to each other.

In one embodiment, as illustrated in FIG. 5 , the head-up displayapparatus is configured so that the angle of reflection a of theprojection light output from the housing 30 through the opening portion32 with respect to a windshield 60 is from 10° to 50°. With suchconfiguration, a head-up display apparatus having more excellentconcealability for its inside and more excellent display brightness canbe achieved by a synergistic effect with the effects of the first andsecond polarizing plates with retardation layers described above. Theangle of reflection a is preferably from 15° to 45°, more preferablyfrom 20° to 40°. The angle of reflection a can be controlled byadjusting the angle of the reflector 20. Specifically, the mirror holderonly needs to be configured so that its angle can be adjusted. Themirror holder has, for example, a shaft whose peripheral surface isconnected to the rear surface of the mirror portion, and a controllingportion connected to an end portion of the shaft. The angle of themirror portion changes following the rotation of the shaft, and hencethe angle of the mirror portion can be indirectly adjusted through thecontrol of the rotation of the shaft by the controlling portion. Theangle of the mirror portion may typically be adjusted in accordance withthe shape of the windshield.

A detailed description of the detailed configuration of the head-updisplay apparatus is omitted because any appropriate configurationcommonly used in the art is adopted. The cover member and the polarizingplate with a retardation layer are specifically described below.

B. Cover Member

As described above, the cover member 40 is typically transparent. Theterm “transparent” as used herein means that the member has a propertyof transmitting visible light having a wavelength of from 360 nm to 830nm. The term “transparent” includes: a case in which the member issubstantially free from absorbing visible light, and transmits lighthaving any wavelength in a visible light region (colorless transparent);and a case in which the member absorbs light beams having somewavelengths in the visible light region, and transmits light having awavelength except the wavelengths (colored transparent). The covermember 40 is preferably colorless transparent. The total lighttransmittance of the cover member is preferably 50% or more, morepreferably 70% or more, still more preferably 90% or more. The totallight transmittance is a value measured in conformity with JIS K 7375.

The surface shape of the cover member may be appropriately set inaccordance with the shape of the opening portion 32. For example, theportion of the cover member configured to cover the opening portion mayinclude only a flat surface or only a curved surface, or the portionconfigured to cover the opening portion may include a plurality of flatsurfaces and/or a plurality of curved surfaces. The surface shape of thecover member typically includes only a flat surface or only a curvedsurface. In the illustrated example, a cover member whose portionconfigured to cover the opening portion includes only a curved surfaceis used.

The thickness of the cover member may be, for example, from 10 μm to1,000 μm. When the cover member is excessively thick, there is a risk inthat the transmittance of the projection light reduces (the light lossof the projection light increases), and moreover, the reduction servesas a cause for the occurrence of a double image. When the cover memberis excessively thin, there is a risk in that its mechanical strengthbecomes insufficient, and hence its covering function becomesinsufficient.

The cover member may include any appropriate transparent material.Typical examples thereof include a resin and glass. Specific examples ofthe resin include: ester-based resins, such as polyethyleneterephthalate and polyethylene naphthalate; cellulose-based resins, suchas diacetyl cellulose and triacetyl cellulose; polycarbonate-basedresins, such as bisphenol A-based polycarbonate; acrylic resins, such aspolymethyl methacrylate; acrylic resins, such as a lactone-modifiedacrylic resin; styrene-based resins, such as polystyrene and anacrylonitrile-styrene copolymer; olefin-based resins, such aspolyethylene, polypropylene, a polyolefin having a cyclic structure or anorbornene structure, and an ethylene-propylene copolymer; vinylchloride-based resins; amide-based resins, such as aromatic polyamide;imide-based resins; sulfone-based resins; polyether sulfone-basedresins; polyether ether ketone-based resins; polyphenylene sulfide-basedresins; vinyl alcohol-based resins; vinylidene chloride-based resins;vinyl butyral-based resins; arylate-based resins; polyoxymethylene-basedresins; and epoxy-based resins. Those resins may be used alone or incombination thereof.

C. First Polarizing Plate with Retardation Layer and Second PolarizingPlate with Retardation Layer

Similar descriptions are applied to the respective constituents of thefirst polarizing plate with a retardation layer and the secondpolarizing plate with a retardation layer (typically the polarizers 124and 54, the first retardation layer 126 and the second retardation layer56, and the substrates 122 and 52), and hence the constituents arecollectively described except for the case where the constituents needto be separately described. For example, the polarizers 124 and 54 maybe identical to or different from each other. The same holds true forthe first retardation layer 126 and the second retardation layer 56, andthe substrates 122 and 52.

C-1. Polarizer

Any appropriate polarizer may be adopted as the polarizer. Typicalexamples thereof include an iodine-based polarizer and a lyotropicliquid crystal polarizer.

A resin film for forming the iodine-based polarizer may be asingle-layer resin film, or may be produced by using a laminate of twoor more layers.

Specific examples of the polarizer formed of a single-layer resin filminclude: a polarizer obtained by subjecting a hydrophilic polymer film,such as a polyvinyl alcohol (PVA)-based resin film, a partiallyformalized PVA-based resin film, or an ethylene-vinyl acetatecopolymer-based partially saponified film, to dyeing treatment with adichroic substance, such as iodine or a dichroic dye, and stretchingtreatment; and a polyene-based alignment film, such as adehydration-treated product of PVA or a dehydrochlorination-treatedproduct of polyvinyl chloride. A polarizer obtained by dyeing thePVA-based resin film with iodine and uniaxially stretching the resultantis preferably used because the polarizer is excellent in opticalcharacteristics.

The dyeing with iodine is performed by, for example, immersing thePVA-based resin film in an aqueous solution of iodine. The stretchingratio of the uniaxial stretching is preferably from 3 times to 7 times.The stretching may be performed after the dyeing treatment, or may beperformed while the dyeing is performed. In addition, the dyeing may beperformed after the stretching has been performed. The PVA-based resinfilm is subjected to swelling treatment, cross-linking treatment,washing treatment, drying treatment, or the like as required. Forexample, when the PVA-based resin film is immersed in water to be washedwith water before the dyeing, contamination or an antiblocking agent onthe surface of the PVA-based resin film can be washed off. In addition,the PVA-based resin film is swollen and hence dyeing unevenness or thelike can be prevented.

A specific example of the polarizer obtained by using a laminate is apolarizer obtained by using a laminate of a resin substrate and aPVA-based resin layer (PVA-based resin film) laminated on the resinsubstrate or a laminate of a resin substrate and a PVA-based resin layerformed on the resin substrate through application. The polarizerobtained by using the laminate of the resin substrate and the PVA-basedresin layer formed on the resin substrate through application may beproduced, for example, by: applying a PVA-based resin solution to theresin substrate; drying the solution to form the PVA-based resin layeron the resin substrate, to thereby provide the laminate of the resinsubstrate and the PVA-based resin layer; and stretching and dyeing thelaminate to turn the PVA-based resin layer into the polarizer. In thisembodiment, the stretching typically includes stretching of the laminateunder a state in which the laminate is immersed in an aqueous solutionof boric acid. Further, the stretching may further include in-airstretching of the laminate at high temperature (e.g., 95° C. or more)before the stretching in the aqueous solution of boric acid as required.The resultant laminate of the resin substrate and the polarizer may beused as it is (i.e., the resin substrate may be used as a protectivelayer for the polarizer). Alternatively, a product obtained as describedbelow may be used: the resin substrate is peeled from the laminate ofthe resin substrate and the polarizer, and any appropriate protectivelayer in accordance with purposes is laminated on the peeling surface.Details of such method of producing the polarizer are described in, forexample, JP 2012-73580 A, the description of which is incorporatedherein by reference in its entirety.

The lyotropic liquid crystal polarizer is excellent in heat resistance,and hence can result in a further improvement in heat resistance of thehead-up display apparatus. The lyotropic liquid crystal polarizercontains, for example, an aromatic disazo compound represented by thefollowing formula (1):

in the formula (1), Q¹ represents a substituted or unsubstituted arylgroup, Q² represents a substituted or unsubstituted arylene group, R¹seach independently represent a hydrogen atom, a substituted orunsubstituted alkyl group, a substituted or unsubstituted acetyl group,a substituted or unsubstituted benzoyl group, or a substituted orunsubstituted phenyl group, M represents a counterion, “m” represents aninteger of from 0 to 2, and “n” represents an integer of from 0 to 6,provided that at least one of “m” or “n” does not represent 0, arelationship of 1≤m+n≤6 is satisfied, and when “m” represents 2, therespective R¹s may be identical to or different from each other.

OH, (NHR¹)_(m), and (SO₃M)_(n) represented in the formula (1) may eachbe bonded to any one of the seven substitution sites of a naphthyl ring.

The position at which the naphthyl group and azo group (—N═N—) of theformula (1) are bonded to each other is not particularly limited. Theazo group is preferably bonded to the 1-position or 2-position of thenaphthyl group.

When the alkyl group, the acetyl group, the benzoyl group, or the phenylgroup represented by R¹ of the formula (1) has a substituent, examplesof the substituent include substituents given as examples of asubstituent in the following aryl group or arylene group. R¹ representspreferably a hydrogen atom, a substituted or unsubstituted alkyl group,or a substituted or unsubstituted acetyl group, more preferably ahydrogen atom. The substituted or unsubstituted alkyl group is, forexample, a substituted or unsubstituted alkyl group having 1 to 6 carbonatoms.

Preferred examples of M (the counterion) of the formula (1) include: ahydrogen ion; an ion of an alkali metal, such as Li, Na, K, or Cs; anion of an alkaline earth metal, such as Ca, Sr, or Ba; any other metalion; an ammonium ion that may be substituted with an alkyl group or ahydroxyalkyl group; and a salt of an organic amine. Examples of themetal ion include Ni⁺, Fe³⁺, Cu²⁺, Ag⁺, Zn²⁺, Al³⁺, Pd²⁺, Cd²⁺, Sn²⁺,Co²⁺, Mn²⁺, and Ce³⁺. Examples of the organic amine include: analkylamine having 1 to 6 carbon atoms; an alkylamine that has 1 to 6carbon atoms and has a hydroxyl group; and an alkylamine that has 1 to 6carbon atoms and has a carboxyl group. When two or more SO₃Ms arepresent in the formula (1), the respective Ms may be identical to ordifferent from each other. In addition, when M of SO₃M in the formula(1) represents a cation that is divalent or more, the cat ion may bebonded to SO₃ ⁻ of any other adjacent azo-based compound molecule toform a supramolecular associate.

“m” of the formula (1) preferably represents 1. In addition, “n” of theformula (1) preferably represents 1 or 2.

Specific examples of the naphthyl group of the formula (1) includegroups represented by the formula (a) to the formula (1) below. R¹s andMs of the formula (a) to the formula (1) are as described for theformula (1).

The aryl group represented by Q¹ in the formula (1) is, for example, afused ring group in which two or more benzene rings are fused to eachother, such as a naphthyl group, as well as a phenyl group. The arylenegroup represented by Q² is, for example, a fused ring group in which twoor more benzene rings are fused to each other, such as a naphthylenegroup, as well as a phenylene group.

The aryl group represented by Q¹ or the arylene group represented by Q²may have a substituent, or may be free of any substituent. Irrespectiveof whether the aryl group or the arylene group is substituted orunsubstituted, the aromatic disazo compound represented by the formula(1), which has a polar group, is excellent in solubility in an aqueoussolvent.

When the aryl group or the aryl ene group has a substituent, examples ofthe substituent include: an alkyl group having 1 to 6 carbon atoms; analkoxy group having 1 to 6 carbon atoms; an alkylamino group having 1 to6 carbon atoms; a phenylamino group; an acylamino group having 1 to 6carbon atoms; a hydroxyalkyl group having 1 to 6 carbon atoms, such as adihydroxypropyl group; a carboxyl group, such as a COOM group; asulfonic acid group, such as an SO₃M group; a hydroxyl group; a cyanogroup; a nitro group; an amino group; and a halogeno group. Thesubstituent is preferably one selected from an alkoxy group having 1 to6 carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms, acarboxyl group, a sulfonic acid group, and a nitro group. The aromaticdisazo compound having any such substituent is particularly excellent inwater solubility. The aryl group or the arylene group may be substitutedwith one kind of those substituents, or may be substituted with two ormore kinds thereof. In addition, the aryl group or the arylene group maybe substituted with the substituent at any ratio.

Q¹ of the formula (1) represents preferably a substituted orunsubstituted phenyl group, more preferably a phenyl group having theabove-mentioned substituent. Q² of the formula represents preferably asubstituted or unsubstituted naphthylene group, more preferably anaphthylene group having the above-mentioned substituent, particularlypreferably a 1,4-naphthylene group having the above-mentionedsubstituent.

An aromatic disazo compound in which Q¹ of the formula (1) represents asubstituted or unsubstituted phenyl group, and Q² thereof represents asubstituted or unsubstituted 1,4-naphthylene group is represented by thefollowing formula (2).

In the formula (2), R¹, M, “m”, and “n” are as described for the formula(1). In the formula (2), A and B represent substituents, and “a” and “b”represent their numbers of substitutions. A and B each independentlyrepresent an alkyl group having 1 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, an alkylamino group having 1 to 6 carbonatoms, a phenylamino group, an acylamino group having 1 to 6 carbonatoms, a hydroxyalkyl group having 1 to 6 carbon atoms, such as adihydroxypropyl group, a carboxyl group, such as a COOM group, asulfonic acid group, such as an SO₃M group, a hydroxyl group, a cyanogroup, a nitro group, an amino group, or a halogeno group. “a”represents an integer of from 0 to 5, and “b” represents an integer offrom 0 to 4, provided that at least one of “a” or “b” does not represent0. When “a” represents 2 or more, the substituents A may be identical toor different from each other. When “b” represents 2 or more, thesubstituents B may be identical to or different from each other.

Of the aromatic disazo compounds included in the formula (2), anaromatic disazo compound represented by the following formula (3) ispreferred. In the aromatic disazo compound represented by the formula(3), the substituent A is bonded to a para position with respect to anazo group (—N═N—). Further, the OH group of the naphthyl group of thearomatic disazo compound represented by the formula (3) is bonded to aposition (ortho position) adjacent to an azo group. The use of sucharomatic disazo compound represented by the formula (3) enables easyformation of a polarizer that is hardly shrunk by heating.

In the formula (3), R¹, M, “m”, and “n” are as described for the formula(1), and A is as described for the formula (2). In the formula (3), “p”represents an integer of from 0 to 4. “p” represents preferably 1 or 2,more preferably 1.

The aromatic disazo compounds represented by the formulae (1) to (3) mayeach be synthesized in accordance with, for example, “TheoreticalProduction Dye Chemistry (Fifth Edition)” written by Yutaka Hosoda(published by Gihodo on Jul. 15, 1968, p. 135 to 152). For example, thearomatic disazo compound represented by the formula (3) may besynthesized by: subjecting an aniline derivative and anaphthalenesulfonic acid derivative to diazotization and a couplingreaction to provide a monoazo compound; then diazotizing the monoazocompound; and subjecting the resultant to a coupling reaction with a1-amino-8-naphtholsulfonic acid derivative.

The lyotropic liquid crystal polarizer may be produced by, for example,a method including a step B and a step C described below. As required, astep A may be performed before the step B, and a step D may be performedafter the step C:

Step A: a step of subjecting the surface of a substrate to alignmenttreatment;

Step B: a step of applying a coating liquid containing the aromaticdisazo compound represented by the formula (1) to the surface of thesubstrate to form a coating film;

Step C: a step of drying the coating film to form a polarizer that is adried coating film; and

Step D: a step of subjecting the surface of the polarizer obtained inthe step C to water-resistant treatment.

(Step A)

The step A is a step of subjecting the surface of the substrate to thealignment treatment to impart an alignment-regulating force to thesurface of the substrate. When a substrate having thealignment-regulating force in advance is used, there is no need toperform the step A. A method of imparting the alignment-regulating forceis, for example, (a) a method including subjecting the surface of thesubstrate to rubbing treatment, (b) a method including forming a film ofpolyimide or the like on the surface of the substrate, and subjectingthe surface of the formed film to rubbing treatment to form an alignmentfilm, or (c) a method including forming a film formed of a photoreactivecompound on the surface of the substrate, and irradiating the formedfilm with light to form an alignment film. When any one of the methods(b) and (c) is used, a polarizing plate with a retardation layer havingthe alignment film between its substrate and polarizer is produced. Thesubstrate may be used as it is (in this case, the substrate may functionas a protective layer for the polarizer), or the following may beperformed: the substrate is peeled, and any appropriate protective filmis arranged on the peeling surface.

(Step B)

The step B is a step of forming the coating film through the use of thecoating liquid. The coating liquid contains the aromatic disazo compoundand a solvent in which the aromatic disazo compound is dissolved ordispersed. The coating liquid is obtained by dissolving or dispersingthe aromatic disazo compound in the solvent. As required, for example,any other polymer except the aromatic disazo compound and/or an additivemay be added to the solvent.

Any appropriate solvent may be used as the solvent in which the aromaticdisazo compound is dissolved or dispersed. An aqueous solvent ispreferred. Examples of the aqueous solvent include water, a hydrophilicsolvent, and a mixed solvent of water and the hydrophilic solvent. Thehydrophilic solvent is a solvent that dissolves in water in anapproximately uniform manner. Examples of the hydrophilic solventinclude: alcohols, such as methanol and isopropyl alcohol; glycols, suchas ethylene glycol; cellosolves, such as methyl cellosolve and ethylcellosolve; ketones, such as acetone and methyl ethyl ketone; andesters, such as ethyl acetate. As the aqueous solvent, water or a mixedsolvent of water and a hydrophilic solvent is preferably used.

The aromatic disazo compound represented by the formula (1) is anorganic compound having lyotropic liquid crystallinity. Accordingly,when the temperature of the coating liquid, the concentration of thearomatic disazo compound therein, or the like is changed, the liquidshows a lyotropic liquid crystal phase. The lyotropic liquid crystalphase is produced by the formation of a supramolecular associate by thearomatic disazo compound in the liquid. The lyotropic liquid crystalphase may be confirmed and identified by an optical pattern observedwith a polarizing microscope. The supramolecular associate is one largecomposite formed by the bonding of a plurality of aromatic disazocompound molecules through a hydrogen bond or the like.

The concentration of the aromatic disazo compound in the coating liquidis preferably adjusted so that the liquid shows a liquid crystal phase.The concentration of the aromatic disazo compound in the coating liquidis typically from 0.05 wt % to 50 wt %, preferably from 0.5 wt % to 40wt %, more preferably from 1 wt % to 10 wt %. In addition, the pH of thecoating liquid is adjusted to an appropriate value. The pH of thecoating liquid is preferably from about 2 to about 10, more preferablyfrom about 6 to about 8. Further, the temperature of the coating liquidis adjusted to preferably from 10° C. to 40° C., more preferably from15° C. to 30° C.

The application of the coating liquid onto the substrate results in theformation of the coating film. In the coating film, the aromatic disazocompound is aligned in a predetermined direction by thealignment-regulating force of the substrate. An application methodincluding using any appropriate coater may be adopted as a method ofapplying the coating liquid. Examples of the coater include a barcoater, a roll coater, a spin coater, a comma coater, a gravure coater,an air knife coater, and a die coater.

(Step C)

The step C is a step of forming the polarizer that is a dried coatingfilm. The formation of the polarizer that is a dried coating film on thesubstrate provides a polarizing plate including the substrate and thepolarizer.

When the coating film obtained in the step B is dried, the solvent inthe coating film volatilizes, and hence a dried coating film (lyotropicliquid crystal polarizer) containing the aromatic disazo compound thatis solid is formed. In the polarizer, the alignment of the aromaticdisazo compound is fixed while the compound forms the supramolecularassociate. A method of drying the coating film is, for example, naturaldrying or forced drying. Examples of the forced drying include dryingunder reduced pressure, heat drying, and heat drying under reducedpressure. The natural drying is preferably used. The drying time of thecoating film may be appropriately set in accordance with the dryingtemperature thereof and the kind of the solvent. In the case of, forexample, the natural drying, the drying time is preferably from 1 secondto 120 minutes, more preferably from 10 seconds to 5 minutes. The dryingtemperature is preferably from 10° C. to 100° C., more preferably from10° C. to 90° C., particularly preferably from 10° C. to 80° C. Thedrying temperature means not the temperature of the surface or inside ofthe coating film but the temperature of the atmosphere under which thecoating film is dried.

(Step D)

The step D is a step of bringing a water-resistant treatment liquid intocontact with the polarizer to impart water resistance to the polarizer.Any appropriate method may be adopted as a method of bringing thepolarizer into contact with the water-resistant treatment liquid.Examples of the contact method include methods such as (a) theapplication of the water-resistant treatment liquid to the surface ofthe polarizer, (b) the immersion of the polarizing plate (polarizer) ina bath filled with the water-resistant treatment liquid, and (c) thepassing of the polarizing plate (polarizer) through a bath filled withthe water-resistant treatment liquid. The application of thewater-resistant treatment liquid described in the (a) may be performedwith, for example, any appropriate coater or spray.

Any appropriate liquid may be used as the water-resistant treatmentliquid. The water-resistant treatment liquid contains, for example, across-linking agent having a function of cross-linking an organic dyeand a solvent in which the cross-linking agent is dissolved ordispersed. The cross-linking agent may be, for example, an organicnitrogen compound, and the solvent may be, for example, an aqueoussolvent. For example, an acyclic organic nitrogen compound having two ormore cationic groups (preferably cationic groups each containing anitrogen atom) in a molecule thereof is used as the organic nitrogencompound. Examples of the acyclic organic nitrogen compound (acyclicaliphatic nitrogen compound) include: an aliphatic diamine, such as analkylene diamine, or a salt thereof; an aliphatic triamine, such as analkylene triamine, or a salt thereof; an aliphatic tetraamine, such asan alkylene tetraamine, or a salt thereof; an aliphatic pentaamine, suchas an alkylene pentaamine, or a salt thereof; and an aliphatic etherdiamine, such as an alkylene ether diamine, or a salt thereof. As theaqueous solvent, the solvent described for the step B may be used.

The concentration of the cross-linking agent in the water-resistanttreatment liquid is preferably from 1 mass % to 50 mass %, morepreferably from 5 mass % to 30 mass %. When the polarizer is broughtinto contact with the water-resistant treatment liquid, an organic dyein the polarizer is cross-linked through the cross-linking agent. Thecross-linking provides a polarizer excellent in water resistance andmechanical strength.

The thickness of the iodine-based polarizer is preferably 15 μm or less,more preferably 13 μm or less, still more preferably 10 μm or less,particularly preferably 8 μm or less. The lower limit of the thicknessof the iodine-based polarizer is 2 μm in one embodiment, and is 3 μm inanother embodiment. The thickness of the lyotropic liquid crystalpolarizer is preferably 1,000 nm or less, more preferably 700 nm orless, particularly preferably 500 nm or less. The lower limit of thethickness of the lyotropic liquid crystal polarizer is preferably 100nm, more preferably 200 nm, particularly preferably 300 nm. When thethickness of the polarizer falls within such range, the projection lightcan be satisfactorily discharged from the housing, and the incidence(passing) of the sunlight into the housing can be suppressed.

The polarizer preferably shows absorption dichroism at any wavelength inthe wavelength range of from 380 nm to 780 nm. The single layertransmittance of the polarizer is preferably from 35.0% to 50.0%, morepreferably from 40.0% to 45.0%.

The polarization degree of the polarizer is 88% or more, and ispreferably 89% or more, more preferably 90% or more.

C-2. Retardation Layers

As described above, the retardation layers each have a function ofconverting linearly polarized light into circularly polarized light orelliptically polarized light, or a function of converting circularlypolarized light or elliptically polarized light into linearly polarizedlight. The refractive index characteristic of each of the retardationlayers typically shows a relationship of nx>ny. As described above, thein-plane retardation Re(550) of each of the retardation layers is from100 nm to 200 nm, preferably from 110 nm to 170 nm, more preferably from130 nm to 150 nm. When the in-plane retardation falls within such rangeas described above, retardation films each having appropriate ellipticalpolarization performance can be obtained with excellent productivity andat reasonable cost. As a result, a head-up display apparatus capable ofsimultaneously satisfying concealability for its inside and displaybrightness can be obtained with excellent productivity and at reasonablecost.

The retardation layer shows any appropriate refractive index ellipsoidas long as the layer has the relationship of nx>ny. The refractive indexellipsoid of the retardation layer preferably shows a relationship ofnx>ny≥nz. The Nz coefficient of the retardation layer is preferably from1 to 2, more preferably from 1 to 1.5, still more preferably from 1 to1.3. The Nz coefficient is calculated from the expression“Rth(λ)/Re(λ)”. The Re(λ) is as described above. The term “Rth(λ)”refers to the thickness direction retardation of a film measured at 23°C. with light having a wavelength of λ nm. When the thickness of thefilm is represented by d (nm), the Rth(λ) is determined from theexpression “Rth=(nx−nz)×d” where “nz” represents the refractive index ofthe film in its thickness direction.

The polarizer and the retardation layer are laminated so that theabsorption axis of the polarizer and the slow axis of the retardationlayer form a predetermined angle. An angle formed between the absorptionaxis of the polarizer and the slow axis of the retardation layer ispreferably from 35° to 55°, more preferably from 38° to 52°, still morepreferably from 40° to 50°, particularly preferably from 42° to 48°,further particularly preferably around 45°. When the first retardationlayer is arranged on an output side with respect to its correspondingpolarizer (side opposite to the display cell) so as to satisfy suchaxial relationship, and the second retardation layer is arranged on aside closer to the inside of the housing with respect to itscorresponding polarizer (side opposite to the cover member) so as tosatisfy such axial relationship, a head-up display apparatus capable ofsimultaneously satisfying concealability for its inside and displaybrightness can be achieved.

The retardation layer includes any appropriate retardation film capableof satisfying such optical characteristics as described above. Typicalexamples of a resin for forming the retardation film include a cyclicolefin-based resin, a polycarbonate-based resin, a cellulose-basedresin, a polyester-based resin, a polyvinyl alcohol-based resin, apolyamide-based resin, a polyimide-based resin, a polyether-based resin,a polystyrene-based resin, and an acrylic resin. When the retardationlayer includes a resin film showing a reverse wavelength dispersioncharacteristic, the polycarbonate-based resin may be suitably used, andwhen the retardation layer includes a resin film showing a flatwavelength dispersion characteristic, the cyclic olefin-based resin maybe suitably used.

The cyclic olefin-based resin is a collective term for resins eachobtained by polymerizing a cyclic olefin as a polymerization unit, andexamples thereof include resins described in, for example, JP 01-240517A, JP 03-14882 A, and JP 03-122137 A. Specific examples thereof includea ring-opening (co)polymer of a cyclic olefin, an addition polymer of acyclic olefin, and a copolymer (typically a random copolymer) of acyclic olefin and an α-olefin, such as ethylene or propylene, and graftmodified products obtained by modifying those polymers with anunsaturated carboxylic acid or a derivative thereof, and hydrogenatedproducts thereof.

As the polycarbonate resin, any appropriate polycarbonate resin may beused as long as the effect of the present invention is obtained. Thepolycarbonate resin preferably contains: a structural unit derived froma fluorene-based dihydroxy compound; a structural unit derived from anisosorbide-based dihydroxy compound; and a structural unit derived fromat least one dihydroxy compound selected from the group consisting of analicyclic diol, an alicyclic dimethanol, di-, tri-, or polyethyleneglycol, and an alkylene glycol or spiroglycol. The polycarbonate resinmore preferably contains: a structural unit derived from afluorene-based dihydroxy compound; a structural unit derived from anisosorbide-based dihydroxy compound; and a structural unit derived froman alicyclic dimethanol and/or a structural unit derived from di-, tri-,or polyethylene glycol. The polycarbonate resin still more preferablycontains: a structural unit derived from a fluorene-based dihydroxycompound; a structural unit derived from an isosorbide-based dihydroxycompound; and a structural unit derived from di-, tri-, or polyethyleneglycol. The polycarbonate resin may contain a structural unit derivedfrom any other dihydroxy compound as required. Details of thepolycarbonate resin that may be suitably used in the present inventionare described in, for example, JP 2014-10291 A and JP 2014-26266 A, thedescriptions of which are incorporated herein by reference.

Specific examples of the cellulose-based resin include cellulose (di ortri)acetate, cellulose propionate, cellulose butyrate, cellulose acetatepropionate, cellulose acetate butyrate, cellulose acetate phthalate, andcellulose phthalate.

The retardation layer (retardation film) is typically produced bystretching a resin film formed from any such resin as described above inat least one direction.

Any appropriate method may be adopted as a method of forming the resinfilm. Examples thereof include a melt extrusion method (e.g., a T-diemolding method), a cast coating method (e.g., a casting method), acalendar molding method, a hot press method, a co-extrusion method, aco-melting method, multilayer extrusion, and an inflation moldingmethod. Of those, a T-die molding method, a casting method, and aninflation molding method are preferably used.

The thickness of the resin film (upstretched film) may be set to anyappropriate value depending on, for example, the desired opticalcharacteristics and stretching conditions to be described later. Thethickness is preferably from 50 μm to 300 μm, more preferably from 80 μmto 250 μm.

Any appropriate stretching method and stretching conditions (e.g., astretching temperature, a stretching ratio, and a stretching direction)may be adopted for the stretching. Specifically, one kind of variousstretching methods, such as free-end stretching, fixed-end stretching,free-end shrinkage, and fixed-end shrinkage, may be employed alone, ortwo or more kinds thereof may be employed simultaneously orsequentially. With regard to the stretching direction, the stretchingmay be performed in various directions or dimensions, such as ahorizontal direction, a vertical direction, a thickness direction, and adiagonal direction. The temperature at which the stretching is performedpreferably falls within the range of the glass transition temperature(Tg) of the resin film ±20° C.

A retardation film (consequently a retardation layer) having the desiredoptical characteristics (e.g., a refractive index ellipsoid, an in-planeretardation, and an Nz coefficient) can be obtained by appropriatelyselecting the stretching method and stretching conditions.

In one embodiment, the retardation layer is produced by subjecting aresin film to uniaxial stretching or fixed-end uniaxial stretching. Aspecific example of the uniaxial stretching is a method involvingstretching the resin film in its lengthwise direction (longitudinaldirection) while running the resin film in its elongate direction.Another specific example of the uniaxial stretching is a methodinvolving stretching the resin film in its lateral direction using atenter. The stretching ratio is preferably from 10% to 500%.

In another embodiment, the retardation layer is produced by continuouslysubjecting a resin film having an elongate shape to oblique stretchingin the direction of an angle θ with respect to its elongate direction.When the oblique stretching is adopted, a stretched film having anelongate shape and having an alignment angle that is an angle θ withrespect to the elongate direction of the film is obtained, and forexample, its lamination with the polarizer can be performed by aroll-to-roll process. As a result, the manufacturing process can besimplified. The angle θ corresponds to such angle formed between theabsorption axis of the polarizer and the slow axis of the retardationlayer as described above.

As a stretching machine to be used for the oblique stretching, forexample, there is given a tenter stretching machine capable of applyingfeeding forces, or tensile forces or take-up forces, having differentspeeds on left and right sides in a lateral direction and/or alongitudinal direction. Examples of the tenter stretching machineinclude a lateral uniaxial stretching machine and a simultaneous biaxialstretching machine, and any appropriate stretching machine may be usedas long as the resin film having an elongate shape can be continuouslysubjected to the oblique stretching.

As a method for the oblique stretching, there are given, for example,methods described in JP 50-83482 A, JP 02-113920 A, JP 03-182701 A, JP2000-9912 A, JP 2002-86554 A, JP 2002-22944 A, and the like.

The thickness of the stretched film (consequently the retardation layer)is preferably from 20 pinto 80 μm, more preferably from 30 μm to 60 μm.

C-3. Substrate

The substrate is an optional constituent of the polarizing plate with aretardation layer, and is arranged as required. The substrate includesany appropriate film that may be used as a protective film for thepolarizer. As a material serving as a main component of the film, thereare specifically given, for example, cellulose-based resins, such astriacetylcellulose (TAC), and transparent resins, such aspolyester-based, polyvinyl alcohol-based, polycarbonate-based,polyamide-based, polyimide-based, polyether sulfone-based,polysulfone-based, polystyrene-based, polynorbornene-based,polyolefin-based, cyclic olefin-based, (meth)acrylic, and acetate-basedresins. There are also given, for example, thermosetting resins orUV-curable resins, such as (meth)acrylic, urethane-based, (meth)acrylicurethane-based, epoxy-based, and silicone-based resins. There are alsogiven, for example, glassy polymers, such as a siloxane-based polymer.In addition, a polymer film described in JP 2001-343529 A (WO 01/37007A1) may be used. For example, a resin composition containing athermoplastic resin having a substituted or unsubstituted imide group ona side chain thereof, and a thermoplastic resin having a substituted orunsubstituted phenyl group and a nitrile group on side chains thereofmay be used as a material for the film, and the composition is, forexample, a resin composition containing an alternating copolymer formedof isobutene and N-methylmaleimide, and an acrylonitrile-styrenecopolymer. The polymer film may be, for example, an extrudate of theresin composition. The (meth)acrylic resin or the cyclic olefin-basedresin may be preferably used.

The glass transition temperature (Tg) of the (meth)acrylic resin ispreferably 115° C. or more, more preferably 120° C. or more, still morepreferably 125° C. or more, particularly preferably 130° C. or more.This is because the resin may be excellent in durability. Although theupper limit value of the Tg of the (meth)acrylic resin is notparticularly limited, the upper limit is preferably 170° C. or less fromthe viewpoint of, for example, its formability.

Any appropriate (meth)acrylic resin may be adopted as the (meth)acrylicresin to the extent that the effects of the present invention are notimpaired. Examples thereof include poly(meth)acrylic acid esters, suchas polymethyl methacrylate, a methyl methacrylate-(meth)acrylic acidcopolymer, a methyl methacrylate-(meth)acrylic acid ester copolymer, amethyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer, amethyl (meth)acrylate-styrene copolymer (e.g., an MS resin), and apolymer having an alicyclic hydrocarbon group (e.g., a methylmethacrylate-cyclohexyl methacrylate copolymer or a methylmethacrylate-norbornyl (meth)acrylate copolymer). Of those, a poly-C₁₋₅alkyl (meth)acrylate, such as polymethyl (meth)acrylate, is preferred.Of those, a methyl methacrylate-based resin containing methylmethacrylate as a main component (from 50 wt % to 100 wt %, preferablyfrom 70 wt % to 100 wt %) is more preferred.

Specific examples of the (meth)acrylic resin include: ACRYPET VH andACRYPET VRL20A manufactured by Mitsubishi Rayon Co., Ltd.; a(meth)acrylic resin described in JP 2004-70296 A, the resin having aring structure in a molecule thereof; and a high-Tg (meth)acrylic resinobtained by intramolecular cross-linking or an intramolecularcyclization reaction.

A (meth)acrylic resin having a lactone ring structure is particularlypreferred as the (meth)acrylic resin because the resin has high heatresistance, high transparency, and high mechanical strength.

Examples of the (meth)acrylic resin having a lactone ring structureinclude (meth)acrylic resins each having a lactone ring structuredescribed in JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP2002-254544 A, and JP 2005-146084 A.

The (meth)acrylic resin having a lactone ring structure has amass-average molecular weight (sometimes referred to as weight-averagemolecular weight) of preferably from 1,000 to 2,000,000, more preferablyfrom 5,000 to 1,000,000, still more preferably from 10,000 to 500,000,particularly preferably from 50,000 to 500,000.

The glass transition temperature (Tg) of the (meth)acrylic resin havinga lactone ring structure is preferably 115° C. or more, more preferably125° C. or more, still more preferably 130° C. or more, particularlypreferably 135° C. or more, most preferably 140° C. or more. This isbecause the resin may be excellent in durability. Although the upperlimit value of the Tg of the (meth)acrylic resin having a lactone ringstructure is not particularly limited, the upper limit value ispreferably 170° C. or less from the viewpoint of, for example, itsformability.

The term“(meth)acrylic” as used herein refers to acrylic and/ormethacrylic.

The cyclic olefin-based resin is as described for the retardation filmsin the section C-2.

When the lyotropic liquid crystal polarizer is adopted, the substratehaving applied thereto the coating liquid containing the aromatic disazocompound may be used as it is as the substrate, or the following may beperformed: the substrate is peeled, and such protective film asdescribed above is bonded to the peeling surface.

It is preferred that the substrate be optically isotropic. The phrase“be optically isotropic” as used herein means that the in-planeretardation Re(550) of the substrate is from 0 nm to 10 nm, and thethickness direction retardation Rth(550) thereof is from −10 nm to +10nm.

The thickness of the substrate is preferably from 20 μm to 80 μm, morepreferably from 30 μm to 60 μm.

C-4. Others

The polarizing plate with a retardation layer may further have a hardcoat layer and/or an antiblocking layer on the opposite side of thesubstrate to the polarizer as required. The hard coat layer is describedin detail in, for example, JP 2007-171943 A. The antiblocking layer isdescribed in detail in, for example, JP 2015-115171A, JP 2015-141674 A,JP 2015-120870 A, and JP 2015-005272 A. The descriptions of thosepublications are incorporated herein by reference.

The polarizer and the retardation layer are bonded to each other via anyappropriate adhesion layer. When the iodine-based polarizer is used, thepolarizer and the substrate are bonded to each other via any appropriateadhesion layer. The adhesion layer may be a pressure-sensitive adhesivelayer, or may be an adhesive layer. A pressure-sensitive adhesiveforming the pressure-sensitive adhesive layer may typically be anacrylic pressure-sensitive adhesive. An adhesive forming the adhesivelayer may typically be an energy ray-curable adhesive.

EXAMPLES

Now, the present invention is specifically described byway of Examples.However, the present invention is by no means limited to these Examples.Evaluation items in Examples are as described below.

(1) Concealability for Inside

A fluorescent lamp (manufactured by Gentos Co., Ltd., “DK-S70CWH”) wasarranged at a position distant from an end of the case (housing) of eachof head-up display apparatus-corresponding products obtained in Examplesand Comparative Examples by 100 mm in a lateral direction and by 400 mmin an upward direction, and the reflection brightness of the bottom ofthe housing was measured with a brightness meter (manufactured by TopconCorporation, “SR-UL1”) under a state in which the power source of theliquid crystal display apparatus of the corresponding product was turnedoff. Further, the viewability of the inside of the housing was visuallyconfirmed, and was evaluated by the following criteria.

∘: The liquid crystal display apparatus in the housing could not beviewed.

x: The liquid crystal display apparatus in the housing was clearlyviewed.

(2) Display Brightness

The display brightness of the liquid crystal display apparatus of eachof the head-up display apparatus-corresponding products obtained inExamples and Comparative Examples was measured with a brightness meter(manufactured by Topcon Corporation, “SR-UL1”).

Example 1

1. Synthesis of Organic Dye (Aromatic Disazo Compound) 4-Nitroanilineand 8-amino-2-naphthalenesulfonic acid were subjected to diazotizationand a coupling reaction by an ordinary method (method described in“Theoretical Production Dye Chemistry Fifth Edition” written by YutakaHosoda and published by Gihodo on Jul. 15, 1968, p. 135 to 152) toprovide a monoazo compound. The resultant monoazo compound wasdiazotized by the ordinary method, and was further subjected to acoupling reaction with lithium 1-amino-8-naphthol-2,4-disulfonate toprovide a crude product. The crude product was salted out with lithiumchloride to provide an aromatic disazo compound represented by thefollowing formula (4).

2. Production of Polarizing Plate

A norbornene-based resin film (manufactured by Zeon Corporation: productname: “ZEONOR ZF14-100”) was prepared as a substrate, and the surface ofthe film was subjected to rubbing treatment and hydrophilic treatment(corona treatment). The aromatic disazo compound represented by theformula (4) was dissolved in ion-exchanged water to prepare a coatingliquid having a concentration of 4 wt %. The coating liquid was appliedto the surface of the substrate subjected to the rubbing treatment andthe hydrophilic treatment with a bar coater (manufactured by Buschman:product name: “Mayer rod HS4”), and was naturally dried in athermostatic chamber at 23° C. to form a dried coating film (polarizer)on the surface of the substrate. The thickness of the polarizer was 300nm.

Subsequently, the laminate having the configuration“substrate/polarizer” was immersed in a water-resistant treatment liquidfor 2 seconds. An aqueous solution containing 1,3-propanediaminehydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.),1,2-ethylenediamine hydrochloride (manufactured by Tokyo ChemicalIndustry Co., Ltd.), and bis(hexamethylene)triamine (manufactured byTokyo Chemical Industry Co., Ltd.) at a mass ratio of 55:15:30 was usedas the water-resistant treatment liquid. The laminate having theconfiguration “substrate/polarizer”, which had been removed from thewater-resistant treatment liquid, was washed with water and dried toprovide a polarizer having imparted thereto water resistance (laminatehaving the configuration “substrate/polarizer”).

3. Retardation Film Forming Retardation Layer

“ARTON 4RJT1403” (manufactured by JSR Corporation) was used as aretardation film forming a retardation layer.

4. Production of Polarizing Plate with Retardation Layer

The laminate having the configuration “substrate/polarizer” and theretardation film were bonded to each other so that the polarizer and theretardation film faced each other. An acrylic pressure-sensitiveadhesive (manufactured by Nitto Denko Corporation, product name:“CS9861UA”) was used in the bonding. In addition, the bonding wasperformed so that the absorption axis of the polarizer and the slow axisof the retardation film formed an angle of 45°. Thus, a polarizing platewith a retardation layer having the configuration“substrate/polarizer/retardation film (retardation layer)” was obtained.The two polarizing plates with retardation layers were prepared, andwere used as a first polarizing plate with a retardation layer and asecond polarizing plate with a retardation layer.

5. Production of Laminate Having Configuration “Second Polarizing Platewith Retardation Layer/Cover Member”

A polycarbonate-based resin sheet having a thickness of 300 μm(manufactured by Mitsubishi Gas Chemical Company, Inc.: product name:“MRF08U”) was used as a cover member. The cover member and the secondpolarizing plate with a retardation layer were bonded to each other viaan acrylic pressure-sensitive adhesive (manufactured by Nitta DenkoCorporation: product name: “CS9862UA”) so that the cover member and thesubstrate faced each other. Thus, a laminate having the configuration“polarizing plate with a retardation layer/cover member” was produced.

6. Production of Head-Up Display Apparatus-Corresponding Product

A case having a size measuring 200 mm by 150 mm by 200 mm, the casehaving an open top, was produced by using carbon-containing conductiveplastic cardboard (manufactured by Yamakoh Co., Ltd.).

Meanwhile, a liquid crystal display apparatus with a backlight was takenout of a portable information terminal (manufactured by Apple Inc.,“i-pad mini”), and its polarizing plate on a viewer side was removed.The first polarizing plate with a retardation layer obtained in theforegoing was bonded to the surface from which the polarizing plate hadbeen removed. The liquid crystal display apparatus having bonded theretothe first polarizing plate with a retardation layer was placed in thecase.

Next, the laminate having the configuration “second polarizing platewith a retardation layer/cover member”, which had been obtained in theforegoing, was used to cover the opening portion of the case so that thecover member faced the outside. At this time, the first polarizing platewith a retardation layer and the second polarizing plate with aretardation layer were arranged so that the absorption axes of theirrespective polarizers were parallel to each other, and the slow axes oftheir respective retardation layers were perpendicular to each other.

Thus, a head-up display apparatus-corresponding product was produced.The resultant head-up display apparatus-corresponding product wassubjected to the evaluations (1) and (2). The results are shown in Table1.

Example 2

A head-up display apparatus-corresponding product was produced in thesame manner as in Example 1 except that both the retardation values ofthe first retardation layer and the second retardation layer were set to110 nm. The resultant head-up display apparatus-corresponding productwas subjected to the same evaluations as those of Example 1. The resultsare shown in Table 1.

Example 3

A head-up display apparatus-corresponding product was produced in thesame manner as in Example 1 except that both the retardation values ofthe first retardation layer and the second retardation layer were set to190 nm. The resultant head-up display apparatus-corresponding productwas subjected to the same evaluations as those of Example 1. The resultsare shown in Table 1.

Example 4

A head-up display apparatus-corresponding product was produced in thesame manner as in Example 1 except that the retardation value of thefirst retardation layer was set to 120 nm, and the retardation value ofthe second retardation layer was set to 190 nm. The resultant head-updisplay apparatus-corresponding product was subjected to the sameevaluations as those of Example 1. The results are shown in Table 1.

Comparative Example 1

A head-up display apparatus-corresponding product was produced in thesame manner as in Example 1 except that the first retardation layer wasnot arranged. The resultant head-up display apparatus-correspondingproduct was subjected to the same evaluations as those of Example 1. Theresults are shown in Table 1.

Comparative Example 2

A head-up display apparatus-corresponding product was produced in thesame manner as in Example 1 except that none of the first retardationlayer and the second retardation layer was arranged. The resultanthead-up display apparatus-corresponding product was subjected to thesame evaluations as those of Example 1. The results are shown in Table1.

TABLE 1 Concealability for inside Retardation Reflection Display layerbrightness Viewability brightness Example 1 140 nm × 2 layers 4 cd/m² ○350 cd/m² Example 2 110 nm × 2 layers 6 cd/m² ○ 347 cd/m² Example 3 190nm × 2 layers 5 cd/m² ○ 345 cd/m² Example 4 120 nm × 1 layer 7 cd/m² ○290 cd/m² 190 nm × 1 layer Comparative 140 nm × 1 layer 4 cd/m² ○ 170cd/m² Example 1 Cover side Comparative None 11 cd/m²  x 348 cd/m²Example 2

As is apparent from Table 1, it is found that each of the head-updisplay apparatus of Examples simultaneously satisfies concealabilityfor its inside and display brightness.

INDUSTRIAL APPLICABILITY

The head-up display apparatus according to the embodiment of the presentinvention may be suitably used in a vehicle including a windshield(typically an automobile).

REFERENCE SIGNS LIST

-   10 display unit-   11 display cell-   12 first polarizing plate with retardation layer-   20 reflector-   30 housing-   40 cover member-   50 second polarizing plate with retardation layer-   100 head-up display apparatus-   101 head-up display apparatus

The invention claimed is:
 1. A head-up display apparatus, comprising: adisplay unit, which includes a display cell and a first polarizing platewith a retardation layer arranged on an output side of the display cell,the first polarizing plate with a retardation layer including apolarizer and a first retardation layer in the stated order from adisplay cell side, and which is configured to output projection light;at least one reflector configured to reflect the projection light; ahousing, which has an opening portion, and which is configured to storethe display unit and the reflector therein; a cover member configured tocover the opening portion; and a second polarizing plate with aretardation layer, which is arranged on a housing inner side of thecover member, and which includes a polarizer and a second retardationlayer in the stated order from a cover member side, wherein the firstretardation layer and the second retardation layer each have an in-planeretardation Re(550) of from 100 nm to 200 nm.
 2. The head-up displayapparatus according to claim 1, wherein the polarizer contains anaromatic disazo compound represented by the following formula (1):

in the formula (1), Q¹ represents a substituted or unsubstituted arylgroup, Q² represents a substituted or unsubstituted arylene group, R¹seach independently represent a hydrogen atom, a substituted orunsubstituted alkyl group, a substituted or unsubstituted acetyl group,a substituted or unsubstituted benzoyl group, or a substituted orunsubstituted phenyl group, M represents a counterion, “m” represents aninteger of from 0 to 2, and “n” represents an integer of from 0 to 6,provided that at least one of “m” or “n” does not represent 0, arelationship of 1≤m+n≤6 is satisfied, and when “m” represents 2, therespective R¹s may be identical to or different from each other.
 3. Thehead-up display apparatus according to claim 1, wherein the polarizerseach have a thickness of from 100 nm to 1,000 nm.
 4. The head-up displayapparatus according to claim 1, wherein the head-up display apparatus isconfigured so that an angle of reflection of the projection light outputfrom the housing through the opening portion with respect to awindshield is from 10° to 50°.